Alaska backcountry expeditionary hunting promotes rapid improvements in metabolic biomarkers in healthy males and females

Alaska Backcountry Expeditionary Hunting Promotes Sustained Muscle Protein Synthesis

INTRODUCTION

We have previously described negative energy balance (ie, -9.7±3.4 MJ/d) and weight loss (Δ-1.5 ± 0.7 kg) influenced by high levels of energy expenditure (ie, 17.4±2.6 MJ/d) during remote expeditionary hunting in Alaska. Despite negative energy balance, participants retained skeletal muscle. The purpose of this pilot study was to measure skeletal muscle protein synthesis and examine molecular markers of skeletal muscle protein metabolism under similar conditions of physical and nutrient stress.

METHODS

The "virtual biopsy method" was used to evaluate integrated fractional synthetic rates (FSRs) of muscle protein from blood samples in 4 participants. Muscle biopsies were taken to measure molecular markers of muscle protein kinetics (ie, FSTL1, MEF2, MYOD1, B2M, and miR-1-3p, -206, -208b, 23a, and 499a) using real-time polymerase chain reaction.

RESULTS

Our findings in 4 participants (2 females [28 and 62 y of age; 66.2 and 71.8 kg body weight; 25.5 and 26.7 kg/m2 body mass index] and 2 males [47 and 56 y of age; 87.5 and 91.4 kg body weight; 26.1 and 28.3 kg/m2 body mass index]) describe mean muscle FSRs of serum carbonic anhydrase (2.4%) and creatine kinase M-type (4.0%) and positive increments in molecular regulation.

CONCLUSIONS

Preservation of skeletal muscle under conditions of physical and nutrient stress seems to be supported by positive inflection of skeletal muscle FSR and molecular activation.

Equivalent servings of free-range reindeer promote greater net protein balance compared to commercial beef

Wild game consumption has been associated with health benefits but the acute influence on human protein metabolism remains unknown. We compared feeding-induced responses of equivalent amounts of free-range reindeer (FR) and commercial beef (CB) on protein kinetics using stable isotope methodology. Seven participants (age: 40 ± 14 years; body mass index: 24 ± 3 kg/m2) completed two randomised studies, ingesting 2 oz of FR or CB. L-[ring 2H5]phenylalanine & L-[ring 2H2]tyrosine were delivered via primed, continuous intravenous infusion. Blood samples were collected during the basal period and following consumption of FR or CB. Feeding-induced changes in whole-body protein synthesis (PS), protein breakdown (PB), and net protein balance (NB) were determined via plasma sample isotope enrichment analysis by gas chromatography-mass spectrometry; plasma essential amino acid (EAA) concentrations were determined by liquid chromatography-electrospray ionisation-mass spectrometry. Plasma post-prandial EAA concentrations were higher with FR compared to CB (P < 0.05). The acute feeding-induced PS response was not different, but PB was reduced and contributed to a superior level of NB (P < 0.00001) in FR compared to CB. Our results demonstrate that FR may influence more favourable protein metabolism than CB. These data support potential health benefits of wild game onf whole-body protein.Abbreviations: BMI: body mass index; DIAAS: digestible indispensable amino acid score; CB: commercial beef; EAA: essential amino acids; FR: free-range reindeer; Ra: rate of appearance; UAF: University of Alaska Fairbanks; USDA: USA Department of Agriculture.

Deterioration of Lipid Metabolism Despite Fitness Improvements in Wildland Firefighters

OBJECTIVE

Determine serum lipid and general health/fitness alterations following a 5-month wildfire suppression season.

METHODS

We recruited 100 wildland firefighters (WLFFs) to a 5-month pre- to post-season observational study. Nude body mass, blood pressure (BP), grip strength, and step-test heart rate (HR) were recorded. Blood samples were collected for lipid panel analysis (total cholesterol, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, triglycerides, triglyceride:HDL-cholesterol ratio). Two-tailed dependent t-tests determined statistical significance (p < 0.05).

RESULTS

There were pre- to post-season changes in nude body mass (+2 ± 4%, p = 0.001), systolic BP (-2 ± 10%, p = 0.01), step-test HR (-5 ± 10%, p < 0.001), and all serum lipids (total cholesterol: +5 ± 14%, p = 0.02, HDL-cholesterol: -1 ± 17%, p = 0.04, LDL-cholesterol: +8 ± 22%, p = 0.02, VLDL-cholesterol: +31 ± 49%, p < 0.001, triglycerides: +30 ± 49%, p < 0.001, triglyceride:HDL-cholesterol ratio: +37 ± 58%, p < 0.001). Pre- to post-season diastolic BP (p = 0.12) and grip strength (p = 0.60) remained stable.

CONCLUSIONS

WLFFs demonstrate maladaptive serum lipids and body mass alterations despite subtle aerobic fitness improvements.